MaxWong

When the number is just a number, i.e. no signs, e.g.: 5, 7, 0.5, they are positive

When the number contains negative sign, e.g.: -1, -2/3, -\(\pi\), they are negative

- 2x + 15 = - 9 | rearrange

15 - 2x = -9 | multiply -1

2x - 15 = 9 | + 15

2x = 24 | /2

x = 12

I love dodos xD

30 + (-50) - 20 <-- the brackets are unnecessary

= 30 - 20 + (-50)

= 10 + (-50)

= 10 - 50

= -40

Same as hectictar's answer.

:D

Use division actually.

'how many time does 7 go into 21 and 49'

Do \(21 \div 7 = 3\\ 49 \div 7 = 7\)

Finish!!

Use logarithms.

x^2 = 2^64 | Take natural log both sides

2 ln x = 64 ln 2 | /2

ln x = 64 ln 2 / 2 | e^ both sides

x = e^(64ln 2/2) = 2^(64/2) = 2^32

x^x = 2^y | natural log again......

x ln x = y ln 2 | substitution

2^32 ln 2^32 = y ln 2 | log property

32 * 2^32 ln 2 = y ln 2 | multiply

2^37 ln 2 = y ln 2 | / ln 2

y = 2^37

Just type 'pi' in the calculator. It understands.

\(2\div 0 = \infty\)

I am assuming that you mean 

For how many values of x is the function \(y=\dfrac{x-2}{x^2-7x+10}\) undefined?

As the denominator is a quadratic function, there are 2 values of x which makes the function \(y=\dfrac{x-2}{x^2-7x+10}\) undefined.

8 * 2 = 16

8 * 5 = 40